1. Field of the Invention
The present invention relates to a method of making a magnetoresistive read element such as a giant magnetoresistive (GMR) element, a tunnel-junction magnetoresistive (TMR) element, and the like. In particular, the invention relates to a method of evaluation for a magnetoresistive read element comprising: a magnetoresistive layered-structure such as a spin valve film, a tunnel-junction film, and the like; a pair of biasing hard layers interposing the magnetoresistive layered-structure therebetween; a pair of electrically-conductive lead layers each connected to the magnetoresistive layered-structure at one end; and a pair of terminal pads each connected to the other end of the electrically-conductive lead layer.
2. Description of the Prior Art
For example, an evaluation method is well known for evaluating magnetoresistive (MR) layered-structure formed on a wafer, as disclosed in Japanese Patent Application Laid-open Nos. 10-294503 and 60-171618. The evaluation method is designed to measure the variation in the magnetoresistance of the magnetoresistive layered-structure. The magnetoresistive layered-structure is put into a magnetic field in the measurement. The inversions of the applied magnetic field acting on the magnetoresistive layered-structure serve to cause the variation in the magnetoresistance of the magnetoresistive layered-structure.
The measurement is conducted on a magnetoresistive layered-structure which is not enclosed within a pair of upper and lower shield layers. The typical magnetoresistive read element is supposed to include the upper and lower shield layers designed to enclose the magnetoresistive layered-structure therebetween. However, the upper and lower shield layers are believed to interfere with the measurement of the magnetoresistance of the magnetoresistive layered-structure, because the upper and lower shield layers serve to shield the magnetoresistive layered-structure from the applied magnetic field. If the applied magnetic field is shielded in this manner, it is impossible to correctly evaluate the magnetic characteristic of the magnetoresistive layered-structure.
Actual magnetoresistive read elements typically employed in final products such as storage devices include a magnetoresistive layered-structure enclosed between upper and lower shield layers. The magnetoresistive read element subjected to the measurement has the structure completely different from that of the actual typical magnetoresistive read elements. However, unless the magnetoresistive read element without the upper and lower shield layers is formed on the wafer, the evaluation cannot be realized on any magnetoresistive layered-structure incorporated in the actual magnetoresistive read elements. Addition of the magnetoresistive read element for the measurement on the wafer leads to a complicated and troublesome manufacturing process.